Patent GB-556363-A (GB)
Title: Improvements in selective shaft positioning apparatus
IPC: G05D3/12
Filed: 1942-03-27
Abstract: 556,363. Electric selective control systems. COLLINS, A. A. March 27, 1942, No. 4099. [Class 40 (i)] Mechanism for variably positioning a shaft, e.g. of a tuning member of a wireless transmitter comprises a number of stop members disposed on the shaft at different angular positions, a corresponding number of cams also disposed at different angular positions on a countershaft, a series of pawls adapted to engage corresponding stop members and means for driving the shaft and countershaft so that the cams on the latter select one pawl and move it into a position to be engaged by its corresponding stop on the shaft. The mechanism, as described, is associated with an electric selective control system, which may also exercise auxiliary control functions, and its operation will first be described with reference to the diagrammatic Fig. 9 which shows the shaft 7 and one stop disc 20a, the countershaft 17 and one cam 21a, and the corresponding pawl 5a. Control is effected by an electrical marking of one contact of switch 58 carried by shaft 17. When the marking. is effected, a reversible motor 2 drives gearing 27, 31, 34 in the direction of the arrows whereby shaft 7 and tuning member 57 are driven through slipping clutch 28 into its home position determined by stop arm 8 and stop 9. At the same time, gear wheel 34 drives, through a slipping clutch 34a, a cam 52 controlling contacts 50 until the cam is stopped by pin 56, the gear 34 however continues to rotate until pin 36 by engagement with dog 37 on the countershaft 17 drives switch 58 to the marked contact. Cam 21a is now in the required position to permit pawl 5a to position itself in the path of stop 20a and the motor is reversed whereupon shaft 7 is driven until stopped by pawl 5a and cam 52 is driven back to stop 54 to disconnect the motor at contacts 50. Construction of selecting mechanism.-Fig. 1 (not shown) comprises a base plate carrying a motor and main driving shaft together with four sets of simultaneously controlled shaft positioning mechanisms and corresponding shafts each comprising the unit shown in Fig. 4 wherein 23 is the main driving shaft. The shaft 7 to be positioned is driven through worm-wheel 27 and slipping clutch, and carries a pile-up of stop discs 20 separated by washers 39 which are keyed to drum 38 secured to the shaft and keyed to a stop arm 8 thereon. The pile up includes a position indicating dial 10 and the position of the stop discs may be adjusted if the securing nut 40 is loosened. The countershaft 17 carrying a pile-up of cams 21 each corresponding to a stop disc is driven by engagement of dog 37 thereon with a pin 36 carried by a gear wheel 34 meshing with gear wheel 31 fixed to worm wheel 27. The cams 21 shaped as shown in Fig. 5 are disposed in different angular positions around the shaft 17 corresponding to the angular positions of the contacts of switch 58. One of the four countershafts drives the slipping clutch member 52, Figs. 7 and 9, which operates the contacts 50. Control circuits, Figs. 10 and 11.-In the first arrangement, Fig. 10, the shaft control switch 58 is marked by a uniselector 63 which is set by impulsing from a transmitter 60 and which may also be used to operate relays 72 ... 75 over contacts 12, 13, 20, 21 of bank 63d for auxiliary controls such as switching on and off, or " C.W. to Phone," at the wireless transmitter. When 74 is operated to switch on, it is held by the switch off relay 75. Impulses from transmitter 60 are repeated by relay 61 to the switch magnet 62 which also operates sluggish relay 67 whereby circuits over the control bank 63d are opened and relay 70 is energized to open the circuit of motor start relay 64. At the end of the impulse train, 67 and 70 fall back and 64 pulls up to cause motor 2 to effect the first of the operations described above in which shaft 7 is homed and countershaft 17 is driven to the contact marked on switch 58. The start relay 64 is first operated over bank 63b and is then held independently over limit switch 50. When the marked contact is reached reversing relay 69 pulls up whereupon the motor drives shaft 7 until it is stopped by the selected pawl and the motor is stopped when limit switch 50 is restored to normal. To perform one of the auxiliary operations, two trains of impulses are transmitted ; the first sets the selector to dead contacts. Relay 71 is a safety relay, normally operated, and serves to prevent undesired operation if the power circuit is interrupted and restored. In the second arrangement, Fig. 11, the setting of the countershaft 17 is controlled by a manually operated switch 76 and a gapped conducting disc 58<SP>1</SP> taking the place of switch 58. Re-setting the manual switch operates relay 79 which starts the motor to drive the countershaft and operate switch 50. When the gap reaches the marked contact, 79 falls back and 80 pulls up to reverse the motor. A supervisory lamp 83 is provided. Contact c of the limit switch may in this case be used to disable the transmitter during timing operations. Specification 556,388 is referred to.